Electromagnetic actuators



M rch 24, 1970 E. R. BURDETT 3,50

ELECTROMAGNETIC ACTUATORS Filed Sept. 25. 1967 2 Sheets-Sheet l INV'ENTOR Edward Raymond Burdett BY Misegades 80 Douglas ATTORNEYS March 24, 1970 E. R. BURDETT ELECTROMAGNETIC ACTUATORS 2 Sheets-Sheet 2 Ill/fl Filed Sept. 25. 19s? I ////r// Al I Ill/If! FIG. 4e

FIG. 4d

US. Cl. 335256 14 Claims ABSTRACT OF THE DISCLOSURE An electromagnetic actuator includes an armature having a permanent or electromagnet positioned between pole pieces of magnetic steel. The armature is slidably mounted in annular end pole pieces of a housing to limit the movement of the armature between two stable positions. Between the pole pieces of the housing is a tubular yoke supporting flux diverting coils spaced apart longitudinally of the housing. Further flux diverting coils are mounted in annular grooves in the pole pieces of the housing.

The armature is maintained in a selected stable position -by the permanent or electromagnet, the armature being movable between its stable positions by appropriately energising the flux diverting coils.

This invention relates to electromagnetic actuators.

One object of the present invention is to provide an improved electromagnetic actuator.

A further object of the present invention is to provide an electromagnetic actuator which can readily be given a long stroke and is particularly suitable for vacuum interrupters.

Yet another object of the present invention is to provide an electromagnetic actuator which may be operated electrically to move in either direction by appropriate energisation from an electrical supply applied to a pair of terminals.

A fourth object of the present invention is to provide an electromagnetic actuator of which the armature is movable between two stable limiting positions and for which both movement and latching in the limiting positions may be effected by appropriate energisation from an electrical supply applied to a pair of terminals.

In accordance with the invention, an electromagnetic actuator comprises a first magnetic member having first and second spaced magnetic parts, a second magnetic member arranged for relative movement between the magnetic parts and forming With the first magnetic member a main magnetic circuit, the second magnetic member having a first pole for close magnetic association with the first magnetic part at a first stable relative position of the magnetic members and having a second pole for close magnetic association with the second magnetic part at a second stable relative position of magnetic members, the first member carrying a pair of first and second pole pieces spaced apart along the direction of relative movement for magnetic cooperation transversely of the direction of relative movement with a part of the said first pole whereby to provide a local magnetic circuit, magnetomotive force producing means for magnetically holding the members in each stable relative position, when achieved, by creating a flux in the main magnetic circuit, and a flux diverting winding disposed between the first and second pole pieces for creating flux in the local magnetic circuit and energisable when the magnetic members are in a particular one of their stable relative positions for causing relative movement of the magnetic members towards the other stable relative position by etfectively di- United States Patent verting the flux created by the magnetomotive force producing means to pass between the said first pole and the forward one of the first and second pole pieces in a direction having a substantial component longitudinally of the relative movement and of appropriate sense.

One embodiment of the present invention will now be described, by way of example, having reference to the ac companying drawings in which FIGURE 1 is a sectional side elevation of an electromagnetic actuator according to the invention; FIGURE 2 is a sectional end elevation on the line X-X of FIGURE 1; FIGURE 3 is a circuit diagram showing how the flux diverting coils are connected to supply terminals and FIGURE 4 shows a series of diagrams used to explain the operation of the actuator.

The electromagnetic actuator incorporates an armature having a tubular permanent magnet 1 positioned between pole pieces 2 and 3 of magnetic steel. A rod of nonmagnetic steel 4 passes through the pole pieces and carries tubes '5, 6 and 7 also of nonmagnetic steel which allow the magnet and the pole pieces to be clamped together by nuts 8 bearing on respective Washers 9. The tubes 5 and 7 are slidably mounted in bearings 10 and 11 provided in annular end pole pieces 12 and 13 respectively of a housing to limit the movement of the armature. Between the pole pieces 12 and 13 is a tubular yoke 14. The yoke 14 is provided at one end with a pair of spaced apart internal annular poles 23 and 24 with a coil 15 mounted therebetween. -A coil 16 is mounted at the other end of the yoke 14 between a similar pair of internal annular poles 25 and 26. The radial length of the poles 23 to 26 is such that a small air gap is provided between the poles and the pole pieces 2 and 3. Further flux diverting coils 17 and 18 are provided in annular grooves formed in the inner surfaces of pole pieces 12 and 13 respectively.

The movement of the armature is controlled by pulses of direct current passed through the flux diverting coils, the supply circuit for the coils being shown in FIGURE 3. Should all the coils be energised at the same time, the magnet 1 would be demagnetised. In order to prevent this diodes 21 and 22 are provided in the circuits of the coils 17 and 18 respectively so that only one of these coils may be operated at any one time.

When it is required to move the armature to the alternative stable position, a pulse is applied between the terminals 19 and 20, the polarity of the pulse being such that terminal 19 is made positive with respect toterminal 20 to energise the coils 15, 16 and 18. As shown in FIG- URE 4, during the initial movement of the armature (FIGURE 4(b)), the flux paths of coils 16 and 18 are open, the downward movement of the armature being caused by the flux in pole 24 being greater than the flux in pole 23. On the armature reaching the mid-position (FIGURE 4(a) the flux path of the coil 16 is closed, the downward movement of the armature being maintained by the flux in poles '24 and 26 being greater than the flux in poles 23 and 25 respectively. Further downward movement of the armature (FIGURE 4(d)) opens the flux path of coil 15 and closes the flux path of coil 18 to increase the flux in the pole piece 13 and move the armature to its alternative stable position (FIGURE 4(e)). On removing the pulse at terminals .19 and 20 the armature is maintained in position by the magnet.

Should it be required to return the armature to its original position, this may be readily accomplished by applying a pulse to the terminals 19 and 20 so that the terminal 20 is positive with respect to the terminal 19'. In this case the diode 22 is switched off and the coils 15, 16 and 17 only are energised.

Due to the high speed of operation, the armature may bounce before finally coming to rest and it may, therefore, be found necessary to ensure that the length of the 3 pulse applied to the terminals 19 and 20 be sufiiciently long to ensure that the armature is brought to rest in the required position.

It has been found that by employing electromagnetic actuators of the type described above, the distances through which the armature may be moved are somewhat greater than those attainable in previously known electromagnetic actuators. Furthermore, by increasing number of coils and associated poles and by appropriately switching the coils, the distance through which the armature is moved may be still further increased. Also the distance through which the armature is moved may be altered by changing the shape of the pole pieces 2, 3, 12 and 13.

Such an actuator is particularly useful for controlling the operation of electric switches where it has been found that there is a requirement to provide greater separation distances between the fixed and movable contacts and also to increase the length of contact wipe between the fixed and movable contacts.

Various modifications may be made without exceeding the scope of the invention. For example, the permanent magnet 1 may be replaced by an electromagnet. Also the pole pieces could be slotted to reduce eddy current losses which tend to slow down the movement of the armature.

I claim:

1. An electromagnetic actuator comprising a first magnetic member having first and second spaced magnetic parts, a second magnetic member arranged for relative movement between the magnetic parts and forming with the first magnetic member a main magnetic circuit, the second magnetic member having a first pole for close magnetic association with the first magnetic part at a first stable relative position of the magnetic members and having a second pole for close magnetic association with the second magnetic part at a second stable relative position of magnetic members, the first member carying a pair of first and second pole pieces spaced apart along the direction of relative movement for magnetic cooperation transversely of the direction of relative movement with a part of the said first pole whereby to provide a local magnetic circuit, magnetomotive force producing means for magnetically holding the members in each stable relative position, when achieved, by creating a flux in the main magnetic circuit, and a flux diverting winding disposed between the first and second pole pieces for creating flux in the local magnetic circuit and energisable when the magnetic members are in a particular one of their stable relative positions for causing relative movement of the magnetic members towards the other stable relative positionby effectively diverting the flux created by the magnetomotive force producing means to pass between the said first pole and the forward one of the first and second pole pieces in a direction having a substantial component longitudinally of the relative movement and of appropriate sense.

2. An electromagnetic actuator according to claim 1, wherein, in addition to the said pair of first and second pole pieces, the first magnetic member further carries at least one other such pair of pole pieces, and a further said flux diverting winding is .individually provided between the pole pieces of each additional pair, the pairs of pole pieces being each arranged for magnetic cooperation transversely of the direction of relative movement with a part of a said pole of the second magnetic member whereby to provide a respective local magnetic circuit, and each further flux diverting winding being successively active to provide further movement of the magnetic members towardthe second stable relative position as the relative movement establishes each second local magnetic circuit in succession, at each such establishment of a local magnetic circuit the flux generated by the magnetomotive force producing means being efiectively diverted to pass between the appropriate said pole of the second member and the forward one of the respective pair of pole pieces in a direction having a substantial component longitudinally of the relative movement and of appropriate sense.

3. An electromagnetic actuator according to claim 1, wherein, in addition to the pair of first and second pole pieces, the first member has a further pair of third and fourth pole pieces spaced apart along the direction of relative movement for magnetic cooperation transversely of the direction of relative movement with a part of the said second pole whereby to provide a second local magnetic circuit which is established by the said relative movement of the magnetic members in response to the energisation of the said flux diverting winding, and a further flux diverting winding is disposed between the pair of third and fourth pole pieces for creating flux in the second local magnetic circuit and energisable for causing further relative movement of the magnetic members towards the other stable relative position by effectively further diverting the flux created by the'magnetomotive force producing means to pass between the said second pole and the forward one of the third and fourth pole pieces in a direction having a substantial component-longitudinally of the relative movement and of appropriate sense.

4. An electromagnetic actuator according to claim 3, wherein the flux diverting winding and, subsequently, the further fiux diverting winding act to provide relative movement of the members from the first stable relative position towards the second stable relative position.

5. An electromagnetieactuator according to claim 4, wherein the physical relationship of the pair of first and second pole pieces to the said part of the first pole when the magnetic members are in the first stable relative position corresponds to the physical relationship of the pair of third and fourth pole pieces to the said part of the second pole when the magnetic members are in the second stable relative position, the flux diverting coil and the further flux diverting coil being e'nergisable with one polarity to act successively to move the magnetic members from the first stable relative position to the second stable relative position, and likewise being energisable with the opposite polarity to act successively in reverse order to move the magnetic members from the second stable relative position to the. first stable relative position.

6. An electromagnetic actuator according to claim 3, wherein the other one of the third and fourth pole pieces forms part of the main magnetic circuit for the first stable relative position of the magnetic members.

7. An electromagnetic actuator according to claim 5, wherein the other one of the third and fourth pole pieces forms part of the main magnetic circuit for the first stable relative position of the magnetic members and the said forward one of the first and second pole pieces forms part of the main magnetic circuit for the second stable relative position of the magnetic members.

8. An electromagnetic actuator comprising a first magnetic member and a second magnetic member movable relative to one another between two stable relative positions and providing in combination a magnetic circuit, the second member having first and second magnetically opposed poles spaced apart along the direction of relative movement and forming part of the magnetic circuit, and the first magnetic member carrying a pole piece for magnetic cooperation transversely of the direction of relative movement with a part of the said first pole, magnetomotive flux producing means for magnetically holding the members in each stable relative position, when achieved, by creating a flux in the magnetic circuit, and a flux diverting winding magnetically associated with the pole piece and energisable for causing relative movement of the magnetic members by effectively diverting the flux created by the magnetomotive force producing means to pass between the first pole and the'pole piece in a direc tion having a substantial component longitudinally of the relative movement and of appropriate sense.

9. An electromagnetic actuator according to claim 1, which includes a latching winding magnetically associated with each magnetic part of the first magnetic member and energisable for augmenting the action of the magnetomotive force producing means magnetically to hold the members in the respective stable relative position when achieved.

10. An electromagnetic actuator according to claim 1, wherein the magnetomotive force producing means comprises a permanent magnet forming part of the second magnetic member and magnetically disposed between the first and second poles.

11. An electromagnetic actuator comprising:

a magnetic housing having first and second opposed magnetic parts supported in spaced relationship by a hollow magnetic yoke,

a magnetic armature disposed within the housing and forming therewith a main magnetic circuit, the armature being arranged for movement between the magnetic parts and having a first pole for close magnetic association with the first magnetic part of the housing at a first stable position of the armature and having a second pole for close magnetic association with the second magnetic part of the housing at a second stable position of the armature, the housing having a pair of first and second pole pieces spaced apart along the direction of armature movement for magnetic cooperation transversely of the direction of armature movement with a part of the said first pole whereby to provide a first local magnetic circuit and having a further pair of third and fourth pole pieces spaced apart along the direction of armature movement for magnetic cooperation transversely of the direction of armature movement with a part of the said second pole whereby to provide a second local magnetic circuit,

magnetomotive force producing means for magnetically holding the armature in each stable position, when achieved, by creating a flux in the main magnetic circuit, and

first and second flux diverting windings disposed respectively between the first and second pole pieces and the third and fourth pole pieces for creating fiux in the respective local magnetic circuits, the first flux diverting winding being energisable with one polarity when the armature is in its first stable position for causing armature movement towards the second stable position by elfectively diverting the flux created by the magnetomotive force producing means to pass between the first pole and the forward one of the first and second pole pieces in a direction having a substantial component longitudinally of the armature movement and in appropriate sense, and the second flux diverting winding being energisable with one polarity when the movement of the armature in response to the energisation of the. first flux diverting winding has established the second local magnetic circuit for causing further armature movement into its second stable position by effectively further diverting the flux created by the magnetomotive force producing means to pass between the second pole and the forward one of the third and fourth pole pieces'in a direction having a substantial component longitudinally of the armature movement and in appropriate sense, the flux diverting coils being likewise energisable with the opposite polarity to act successively in the reverse order to move the armature from the second to the first stable position, the pole pieces mechanically involved in. causing such armature movement being, in succession, the other ones of the third and fourth pole pieces and the first and second pole pieces.

12. An electromagnetic actuator according to claim 11, which includes a latching winding magnetically associated with each magnetic part of the housing "and energisable for augmenting the action of the magnetomotive force producing means magnetically to hold the armature in the respective stable position when achieved.

13. An electromagnetic actuator according to claim 12, wherein the latching windings are connected in parallel between first and second terminals for supply from a common reversible supply, and a diode gating means is connected in series with each latching winding for preventing energisation of the respective latching winding when the other latching winding is energised to augment the action of the magnetomotive force producing means magnetically to hold the armature in the respective stable position.

14. An electromagnetic actuator according to claim 13, wherein the flux diverting windings are also connected for supply between the first and second terminals.

References Cited UNITED STATES PATENTS 3,202,886 8/1965 Kramer 335-268 XR 3,184,410 5/1965 Flora 335-256 XR 3,148,292 9/1964 Bergslien et a1. 335266 XR 2,915,681 12/1959 'Troy 335229 XR BERNARD A. GILHEANY, Primary Examiner D. M. MORGAN, Assistant Examiner U.S. Cl. X.R. 335-266 

